I agree that PI is a good example of a well designed skill, but I also agree that it could be cut just for hotbar bloat.

I've only ever used the skill for Valigarmanda EX and Shadowcaster in criterion. I don't feel like WHM ever says "I wish that heal had more potency". First you need to be in a situation where you're planning (planning!) on casting 2-3 GCD heals in a row. And that is never in dungeon or trials, very rare in extremes, but potentially critical in savage and criterion. Actually I take back what I said about PI being good design. If it was good then it wouldn't be so rarely useful.